The present invention relates to pseudomycin natural products including pseudomycins Axe2x80x2 and Bxe2x80x2, methods for making such pseudomycins, and methods employing antifungal activity of these pseudomycins.
Fungal infections are a significant cause of disease, degradation of quality of life, and mortality among humans, particularly for immune compromised patients. The incidence in fungal infections in humans has increased greatly in the past 20 years. This is in part due to increased numbers of people with immune systems weakened or devastated by organ transplants, cancer chemotherapy, AIDS, age, and other similar disorders or conditions. Such patients are prone to attack by fungal pathogens that are prevalent throughout the population but are kept in check by a functioning immune system. These pathogens are difficult to control because some existing antifungal agents are either highly toxic or only inhibit fungal activity. For example, the polyenes are fungicidal but toxic; whereas, the azoles are much less toxic but only fungistatic. More importantly, there have been recent reports of azole and polyene resistant strains of Candida which severely limits therapy options against such strains.
Pseudomonas syringae produce several classes of antifungal or antibiotic agents, such as the pseudomycins, syringomycins, syringotoxins, and syringostatins, which are lipodepsinonapeptides. Natural strains and transposon generated mutants of P. syringae produce these lipodepsinonapeptides. Several of the pseudomycins, syringomycins and other lipodepsipeptide antifungal agents have been isolated, chemically characterized, and shown to possess wide spectrum antifungal activity, including activity against important fungal pathogens in both humans and plants. For example, pseudomycins A, B, C and Cxe2x80x2 have each been isolated and purified and their structures have been characterized by methods including amino acid sequencing, NMR, and mass spectrometry. See, e.g. Ballio et al., xe2x80x9cNovel bioactive lipodepsipeptides from Pseudomonas syringae: the pseudomycins.xe2x80x9d FEBS Lett. 355, 96-100 (1994) and U.S. Pat. No. 5,576,298. The pseudomycins, the syringomycins, the syringotoxins, and the syringostatins represent structurally distinct families of antifungal compounds.
None of the pseudomycins, syringomycins, syringotoxins, or syringostatins has been brought to market for antifungal therapy. Discovery of undesirable side effects, making formulations, scaling up production, and other development problems have thus far prevented exploitation of the pseudomycins, syringomycins, syringotoxins, or syringostatins against the full range of fungal infections that affect animals, humans and plants. There remains a need for an antifungal agent that can be used against infections not treated by existing antifungal agents and for application against infections in animals, humans, or plants.
The present invention provides a pseudomycin natural product produced by P. syringae. The pseudomycin natural product includes a depsinonapeptide ring with the sequence Ser-Dab-Asp-Lys-Dab-aThr-Dhb-HOAsp-ClThr, more specifically, L-Ser-D-Dab-L-Asp-L-Lys-L-Dab-L-aThr-Z-Dhb-L-Asp(3-OH)-L-Thr(4-Cl), with the carboxyl group of the ClThr and the hydroxyl group of the serine closing the ring with a lactone bond. Pseudomycin Axe2x80x2 (IA) includes a 3,4-dihydroxypentadecanoic acid moiety, the carboxyl group of which forms an amide bond with the amine group of the N-terminal serine. 
Pseudomycin Bxe2x80x2 (IB) includes a 3-hydroxydodecanoic acid moiety, the carboxyl group of which forms an amide bond with the amine group of the N-terminal serine. 
The invention also relates to methods employing a pseudomycin natural product, such as pseudomycin Axe2x80x2, pseudomycin Bxe2x80x2 or a mixture thereof, for inhibiting fungal activity or for reducing the symptoms of a fungal infection in a patient in need thereof. Such methods can kill the fungus, decrease the burden of a fungal infection, reduce fever and/or increase the general well being of a patient. The methods of the invention are effective against fungi such as Candida parapsilosis, Candida albicans, Cryptococcus neoformans, and/or Histoplasma capsulatum.